Alkylation process



March l1, 947..

C. E. HEMMINGER ALKYLATION PROCESS Filed bot. 22, 1942 .VBS ma.

Patented Mar. 11, 1947 diaries. ,Hemmingen weitet, @einer toStandardvOil Development Company; a corporation of Delaware ppli-cationctober 22, 1942, Serial o.42,8

The present inyention relates to improvements inthe ait of th a1ky1ationof oiens with isoparains and, more particularly, it relates toimprovements in 'the process o f producing an alkylate boiling withinthe gasoline 'range from an olefin and isobutane employing weakersulfurie acid and higher temperatures than have heretofore beenemployed.

Asis generallyl known, branch chain hydrocarbons boiling within thegasoline range and haring an octainenurhber of 1 00 or higher may beproduced Aby reacting together an isoparafn, such as isobutane, with anolefin, such as butylene in the presence ofstrong sulfuric acid, saylacid or 9e- 100% strength, at temperatures o f the order ff vabout F.It has been found that the alkylation process previously indicatedcarriedoutcontinuously that improvement in both quality rand yield risYmaintained by maintainingn'in the reaction Zone a relatively largei'riole'cular 'ecess of isobutane over the olefin. For'exanple, where'fat least 50 mois of the isoparaffnare present for eachniol of theolefin in thealkylation Vzone good results are obtained in that ytheyields are improved and the quality of the product is 'improved overprocesses in which the molecular excess of the isoparain issubstantially less. v Y I` have lnov) follnd that by employing C3 andCato C7 oIens, aswell 'as C4'o1ens and by operyating yat highertemperatures during the alkyla- 'tion of theCa and C's t C7 lens, thancustomaruyf'eiiiployed during C4 folen'n aikyianon; 1 may employsulfuric acid of 'l5-85 weight per cent l'and thereby eect considerableeconomy of operation, as regards acid consumption. For example, intheusual process of preparing an alkyllatedfrom isobutane and butyleneemploying strong sulfuricacid of say 98%, and withdrawing acid at 92%strength, the acid consumption is of the order of 1.2 lbs. of acid pergallon of allg'ylate 1:ro'd1 .1.ced--v I have found that I may re- -ducethis acid y consumption to 0.8 lb. of acid of 35% strength perfgallon ofvalkylate produced. AI 1have ils'o-fcuii1d that by decreasing theexternalrat'io 'of isopar'afn to olen to within the 'range of from y2-4mols of vis'op'arailin `per molof volen, I may'also increase theproduction of the alkylate per volume of isobutane which Ais usually thecritical material for alkylation. Thus, I vmay "reduce the isobutanerequirement from 1.125Iv gallons of isobutane to about 1 gallon ofisobutane by my improved process.

I Ihave further found 'that the most desirable 4 claims. (c1. tsaii)ploy as' a 'feed stock a cnt or 'fraction say from a catalyticcracliiingoperation containing C3, C4, C5, C, and Ci hydrocarbons. According to mypreferred procedure, the C4 hydrocarbons are alkyl'ated under the usualalkylatingconditions, that is, employing strong acid (over 92%). The C3hydrocarbons and the lower boiling 'portionof the C5 hydrocarbons, arethen alkylated with the spent butene alkylation acid until itsconcentranon is reduce'dt about 8o to 90%, a5 %v preferred weight percent. The balance of therCs, C, and C1 hydrocarbons are thenalkylatedwith an 'acid vof about 75% strength. This series of operation reducedthe 'acid con'sur'nptionper unit of hal alkylate to about 'one-half ofvthe amount previously employed, and also gives a greater yield ofalkylates, since saturated products are obtained Yfro'rri the C, C,andC'v Olens Withthe corrsumptiori of lower amounts of isobutan'e thanusual, the remainder being available for alkylation of the C and C4olens. The spent acid from the 75% strength alkylatioh 0f the heavyolens may be used to pretreat theheavier olefins to remove the dienes soas to reduce the acid consumption in the alkylation step. Thispretreating is preferably accomplished with' acid :d'iluted to iiD-%strength.

The main object of my present `invention, therefore, is to devise aprocess Yfor alkyl'ating a relatively Wide range of olenic hydrocarbons,that is from C3 to C7 olens, in stages, 'employing the spent acid fromone vstage vas the alkylat'- ving catalyst in another stage, thusreducing v"substantially the acid consumption and effecting appreciableeconomy.

Another object offthis invention is to provide alkylation techniqueadapted to obtain the maximum amount of alkylate from a given amount ofisobutane.`

Other and further objects of my invention 'will appear fromthe followingmore detailed description and claims. o

In the accompanying drawing', I have shown a Vflow plan which indicates'diagrammatically fa preferred method of earryingmy invention Yintopractical effect.

I shall no wsetoforth a specific example or my inventionhan'd refertothe drawing. It willrbe understood that the following details are'purely for purposes of illustration and not not impose `any limitationon my invention. o

In reference to the drawing, the lighter ends of 'a crackedpe'troleu'rn'gas oil vwere introduced into the present Is'y'slter'nthrough line yI `4andthfen'ce dschard into a ra'ct'nathg rcol'ifnn"'3"'yvhere the cracked stock was fractionated as below indicated. The feedstock in line I contained Cs, C4, C5, Cs and C'z hydrocarbons and in thefractionating column the C4 hydrocarbons containing butenes were takenoff as aside stream through line 4 and then discharged along withisobutane present in the C4 hydrocarbons and 4recycled isobutanefedthrough line 5 to line 4 into an alkylation reactor vI 'where theywere treated n with sulfuric acid of from 92% to 95% at a temperature of35-85 F. for a sui'licient period of time to effect the desiredconversion. The alkylationV of the C4 hydrocarbons was carried out inknown manner with the usual recycling of unreacted isoparaihn to thereaction Yzone from a distillation zone, and the process was otherwiseoperated according to known methods. It will be understood that if thereis insufficient isobutane in the feed Vin line I, additional isobutanemay be fed from some outside source to the system through line 6. I haveshownv a settling drum 8 and a raw alkylate draw-off pipe I0, as well asan acid draw-off line I2. The raw alkylate in line IIIk was delivered toa fractionator I5 where it Ywas freed from isobutane, removed throughline I8 and recycled through lines 5 and I I to reactor 'Land thencedischarged'into a second fractionator` 25 from which normal butane wasremoved through line 2l. The raw alkylate was withdrawn through line 29.It will be understood that the produ :t withdrawn'through line 29 wasdelivered to conventional neutralizing, washing and distillation'equipment to produce a finished alkylate in apparatus not'shown. Thespent acid in line I2 was in part'recycled to the alkylation zone l, butanother portion of the spent acid was withdrawn through line I4. As isconventional, fresh acid was discharged from linel I6 into line I2 tofortify the acidre-entering alkylation zone intoV the alkylation zone 30as shown. In alkylation zone 30 the temperature was maintained in therange of'frcm about 45"v F. to 100 F. Here, the ratio of acid to total'hydrocarbon was from 100 to 500, and the external ratio of isoparafn toolen'was from'3 to 6 isoparaflin per mol of olefin. The isoparafiln inthis case wasV supplied from extraneous sources and was introduced intoline 20 throughline-2|. However,

4some of the isobutane in line 5 may bei'withdrawn through line I9 anddischarged into line 25 entering the reaction zone 30; I'he alkylationproduct was withdrawn through line32 and dischargedinto asettling drum34. The raw alkylate was-withdrawn through line'35 and delivered tofractionators l5 and 25 through line 3'I'to r cover isobutane forrecycling to the system. The y acid, on the other hand, was withdrawnthrough 4line 38 and recycled in part to line I4 entering alkylationzone 30.' However, a major portion of this acid, which has aconcentration of about- V85% by weight, was withdrawn through lineJlIland mixed with bottoms withdrawn from column 3 through line 4Z in amanner which will be vpres-V .The acid inline I4 had' aV strength ofabout 'y ing of gases.

ently described more fully. The bottoms from line 42 contained thatportion of the C5 cut not withdrawn through line 22, together with theCs and C7 hydrocarbons and these were discharged into an alkylation zone43 along with extraneous isobutane through line 44 and/or isobutanewithdrawn from line 5 through line 9 where they were admixed with theacid discharged therein throughline 40. The temperature conditionsprevailing in alkylation zone 43 were from 507 to 110 F.; the ratio ofhydrocarbon to acid was about 2-5 parts by weight ofV hydrocarbon(total) per part of acid; and under these conditions an alkylationproduct was formed which was withdrawn eventually through line 50 anddischarged into a settling Vzone 52 from which the separated rawalkylate was Withdrawn through line 55 and delivered, rst toVfractionators I5 and 25 and then delivered to finishing equipment torecover the desired product. The spent acid, on the other hand, which`had a strength of about '75% by weight, was withdrawn from settling Zone52'through line B0. V'This `acid may be employed after dilution to about65% `to treat the heavier olens in line 42 to remove diolens therefrom.

In reaction zone 43 and valso in reaction zone 30, the ratio ofisobutane toolen entering the said reaction zones was preferably from2-5 mols of isobutane per mol of olefin and not more than 6 mols ofisobutane per mol of olefin. In both zones some parans were'form'ed byolefin polymerization, accompanied by carbon schismand hydrogentransfer.

It will be understood that the specific example which I have set forthabove is Vpurely illustrative and numerous modifications of theinvention may be madewithout departing from-the'spirit thereof. Forexample, I may employ some other Y alkylation catalyst than sulfuricacid, such as Vthe oxides of phosphoric acid, or sulfuric acidcontaining boron fluoride, nickel sulfate or hydrochloric acid. Also,thefeed stock mayv be a `different ycomposition than that previously'indicated' or vfrom other sources such zas' thermal cracking orreforming petroleum cuts or crack- To recapitulate, my invention residesinobtaining a greater amount of alkylate vfrom a given amount ofisobutane and involves converting at least some'of the 'olens availablein a renery, into saturated branched chain paraflinsV by Vpolymerizationand inter-polymerization `of said olens, accompanied by somealkylation-with isobutane. The possibility of obtaining Darafiins fromoleiins` by polymerization accompanied.I by

hydrogen transfer underA the conditions ,describedy vto increase yields..Inall stages, 'ItV employ lower isobutane to olefin ratios thannormally employed in alkylating C4 hydrccarbons I iamrjen'abled thus, toincrease the .overall yield of desired product over thatobtainablefromalkylating merely the C4 or Cs olenic Yhydrocarbonsjaccording toknown procedure. f Y i c Y 'Io illustrate thewadvantage ofrmyjinventlon:

When gallons/of a mixtureofolefins Ccontaining 20 gallons of C3 olefins,'gallons'Crolens, 30 gallons Csjolyensw and15jgallonsCsand Cn olensareralkvletedungeri theionventinal operating conditions for alkylatingbutylene, where 90% or stronger sulfuric acid is used, with 6:1isobutane to olefin molal ratio (external) and temperatures f 35 F.,about 120 gallons of isobutane are consumed. However, following theprocess steps described above, only about 90 gallons of isobutane arerequired. Of course, the yield oi aviation alkylate is less, namelyabout 14() gallons of compound to 160 gallons when the larger amounts ofisobutane are required. However, this yield is greater than if only theproportional part of olens were alkylated under usual conditions, namelyabout 120 gallons. On the other hand, if the same quantity of isobutanewere used, 125 gallons, and excess olefins were available, the usualcase in refinery balances, the alkylate yield would be 185 gallons.Thus, with the same size alkylate plant 185 gallons rather than 160gallons are produced from the same amount of isobutane by thisinvention. The quality of the alkylate I produce in blends of highquality aviation gasoline containing tetraethyl lead is oi' the samequality as where only the C4 olens are employed.

Many modifications of my invention will occur to those familiar with theart. I am aware that I may not claim alkylation broadly, but I claim:

1. A combined method of converting a hydro-- carbon fraction containingCs to C1 oleiins into substantially saturated hydrocarbons boiling inthe gasoline range comprising alkylating the C4 oleiins from the C3 toC7 fraction with isobutane in the presence of concentrated sulfuric acidof alkylation strength in a first stage and alkylating the C3 and C5 toC1 olens from this fraction with isobutane in the presence oi sulfuricacid of alkylation strength less concentrated than said concentratedsulfuric acid at a temperature above 35 F. in a second stage andmaintaining the external isoparaliin t0 olefin ratio lower in the secondstage than in the iirst stage.

2. A continuous method for producing branch chain parain hydrocarbonswhich comprises fractionating a feedstock containing Cs to C7 olefinichydrocarbons and isoparafns into an overhead fraction containing C3hydrocarbons, a rst side stream containing the C4 hydrocarbons, a secondside stream containing the C5 hydrocarbons, and a bottoms fraction,combining the overhead fraction with the second side stream fraction,alkylating the C4 hydrocarbons in the presence of strong sulfuric acid,alkylating the combined overhead and second side stream fraction withthe spent acid from the alkylation of the C4 hydrocarbons and alkylatingthe bottoms fraction with the spent acid from the alkylation oi thecombined overhead and second side stream fraction, and maintaining theexternal isoparafn to oleiin ratio lower in each succeeding Zone in thedirection of flow of the acid than in the preceding zone.

3. A continuous method for producing branch chain paraffin hydrocarbonswhich comprises iractionating a feedstock containing C3 to C7 olenichydrocarbons and isoparains into an overhead fraction containing C3hydrocarbons, a irst side stream containing the C4 hydrocarbons, asecond side stream containing C5 hydrocarbons and a bottoms fraction,combining the overhead fraction with the second side stream fraction,alkylating the C4 hydrocarbons in the presence of 92 to 95% sulfuricacid at a. temperature between 35 and 85 F. with an external isoparaiiinto olefin ratio of 6 to 1, and alkylating the combined overhead andsecond side stream fractions with sulfuric acid having a concentrationbetween 80 and 90 at a temperature between 45 and 100 F., using anexternal isonaraiiin to olen ratio of between 3 and 6 to l andalkylating the bottoms fraction with a suluric acid having aconcentration of about at a temperature between 50 and 110 F., and usingan external isoparain to olen ratio between 2 and 4 to 1.

4. The method set forth in claim 2 in which the temperature in theseveral zones is progressively increased in accordance with themolecular weight of the olens undergoing alkylation.

CHARLES E. I-IEMMINGER.

REFERENCES CTTED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,267,457 Goldsby Dec. 23, 19412,256,615 Hederhorst Sept. 23, 1941 FOREIGN PATENTS Number Country Date515,367 British Dec. 4, 1939

